Building on previous observations, a group of scientists in the Department of Gerd Jürgens at the Max Planck Institute for Developmental Biology, together with scientists in Belgium, described the necessity of combining increased cell cycle activity and auxin, which is one of the major plant hormones, to give rise to an increase in root branching.

The researchers found that GAs interact with other plant hormones such as auxin to tell the plant whether to concentrate on reaching for the sky or on building a bigger, better network of roots under ground.

These facts made me think that there must be a plant hormone, other than auxin, that is capable of inhibiting shoot branching-a branching-inhibiting hormone that this did not function in the mutant, resulting in excess shoot branching. "